1. Field of the Invention
The present invention relates to a caterpillar, and more particularly to a fixing structure used to fixing a pin with a link in the caterpillar.
2. Background of the Invention
In general, caterpillar type vehicles, such as heavy equipment containing bulldozers, hydraulically operated shovels and the like, have caterpillars, wherein each the caterpillar has an endless link chain 51 comprising a series of links, as shown in FIG. 12, wherein on each the link a tread plate (not shown) for traveling on the ground may be mounted. The link chain 51 has links 52a and 52b that are substantially parallel and opposing to each other, with the link chain provided with a connecting means 54 for pivotally connecting links 52a and 52b. The links 52a and 52b respectively has a middle portion 55 with the not shown tread plate mounted thereon and connecting portions 56 and 57, wherein these portions 56 and 57 extend from the opposite ends of the middle portion 55, wherein the portion 56 is disposed inside the center line L of the link 52a or 52b and the portion 57 is disposed outside the center line L of the link. The connecting portion 56 is provided with a pin inserting bore 58, and the connecting portion 57 is provided with a bush inserting bore 59. The connecting means (connecting mechanism) 54 has a pin 60 and a bush fitted thereon.
In assembling of the traveling caterpillar, the first bush 61 disposed between the connecting portions 57,57 of the oppositely disposed links 52a, 52b, second each end of the bush 61 is inserted into the bush inserting bore 59 of each side, with the pin 60 having been inserted into the bush 61. Opposite end portions of the pin 60 that are protruded from the bush 61 are inserted into inserting bores 58 of the other links 52a and 52b to be connected, thereafter links 52a or 52b (general symbol: 52) are firmly connected with the pin 60 by means of fixing structure 62 shown in FIG. 13.
Fixing structure 62 functions in such a manner that when an escape-preventing ring 64 is fitted into a space 63, this escape-preventing ring 64 limits escaping relative motion of the pin 60 with respect to link 52 toward off-opening side (receding direction), wherein the fixing structure 62 is formed with an annular space 63 between the periphery of an opening (herein after, mentioned as an opening-periphery) of the pin inserting bore 58 and end portions of the pin. On the end portion of the pin, a peripherally extending concave groove 65 is formed, while on the opening-periphery of the pin inserting bore 58, a tapered surface 66, which narrows (decrease its diameter) inwardly along the longitudinal direction of the bore 58, is formed, so that the space 63 is formed by the tapered surface 66 and the peripherally extending concave groove 65.
However, in the fixing structure described above, the escape-preventing ring 64 fitted into the space 63 may act as a wedge such as would exerts comparatively large tensile stress around the peripherally extending concave groove 65. This kind of pin 60 usually produced having comparatively high hardness, such as, for example, ranging from 50 to 65 as measured by HRC scale, therefore, the escape-preventing ring 64 can cause brittle fracturing of the bottom surface of the peripherally extending concave groove 65 when the escape-preventing ring 64 is fitted into the groove, causing stable fixing state to be hardly maintainable.
In view of the above, the present invention is intended to overcome above problems, and it is an object of the present invention to provide a new and improved fixing structure for connecting the pins with the links in the caterpillar, allowing the caterpillar to have stabilized durability for a long period.